Kritosaurus, meaning “separated lizard” (sometimes misinterpreted as “noble lizard”), is a genus of duckbilled dinosaur from the Late Cretaceous Period (73 million years ago). It lived, possibly, in both North and South America. It was discovered in 1904 by Barnum Brown near Ojo Alamo, New Mexico. The initial discovery could not be verified age-wise, but by 1916 Brown was able to determine it came from the late Campanian age of the Kirtland Formation. It was initially named Nectosaurus, but since that name was already taken, it was renamed to Kritosaurus. The type species is K. navajovius. There are two other known species: K. incurvimanus, and K. notabilis. A fourth specimen, Hadrosaurus breviceps, was formerly assigned to Kritosaurus, but is no longer accepted.

Other specimens have been assigned to Kritosaurus in the 1970s and early 80s, all of which were later placed within other genera. In 1984, another species, K. australis, was introduced to the world. It is unknown if this species belongs to the Kritosaurus genus. In 1990, Jack Horner and David B. Weishampel separated Gryposaurus from Kritosaurus, stating that there was much uncertainty with the skull fragments. Two more skulls were described in 1992 by Horner. They were initially placed in the genus Kritosaurus, but the following year Adrian Hunt and Spencer G. Lucas put the skulls into two distinct genera. This has come with much debate. At least a few other paleontologists agree with Horner’s original findings.

Kritosaurus is known from only a partial skull and lower jaw. Other materials found only add minuscule details at best. The nominate skull is about 34 inches long from the tip of the beak to the back of the skull. It was a flat-headed or crested duckbill. It is poorly known, and its closest relatives are not yet known, however it shares similarities with the Canadian Gryposaurus. A nasal crest may have been used for different social functions, such as sexual identification or social ranking. There may have been inflatable air sacs along the crest used for both visual and auditory signaling.

Kritosaurus was a large bipedal/quadrupedal herbivore. It ate plants with a complex skull that allowed for the chewing and grinding of food. Its teeth were continually replaced throughout life. It would have cropped plant material with its broad beak and held it in place in its cheek-like jaws while chewing. It would have browsed food from the ground up to a height of about 13 feet.

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